Lumber processing is highly automated and in certain processing stations, the boards need to be precisely spaced apart on the conveyor when entering a station. To achieve this spaced relationship, the boards are commonly transferred from a conveyor where the boards are in close or abutting relationship onto a second conveyor having lugs that determine the desired spacing. A transfer mechanism controls the transfer from one conveyor onto the other to assure the relationship desired.
A typical transfer mechanism employs an intermediate pick off wheel and a stop member. The board movement is stopped on the first conveyor (although the conveyor typically continues to slide under the boards) and each leading board in turn is picked off the first conveyor by the pick off wheel and carried over onto the next conveyor in timed sequence.
U.S. Pat. Nos. 2,980,234 and 6,431,345 both describes a transfer mechanism that lifts the forward bottom edge of a board over a stop in order to transfer the board from a first conveyor to a second conveyor.
It is generally a requirement to stop the feeding of lumber without stopping the lugged conveyor. This can be accomplished by having moveable stops hold back the layer of boards so as to not engage the pickoff wheel or feed mechanism. Alternately, the feed wheel can be stopped with a mechanical clutch arrangement. The clutch must be of a type to engage or disengage at a fixed rotary position relative to the rotation so as to maintain the timing of the feed to the lugs. The first means has problems operating at high speeds because the time available to activate the moveable stops becomes too short or limited. The second means has a problem with the fixed or even finite multiple fixed engagement/disengagement positions not being adequate to allow for a wide speed variation of the lugged conveyor.